Fasteners and fastener delivery devices for affixing sheet-like materials to bone or tissue

ABSTRACT

A fastener for attaching a sheet-like implant to tissue or bone may be provided with a first arm having a proximal portion and a distal portion, a second arm having a proximal portion and a distal portion, and a bridge formed at least in part by the proximal portion of the first arm overlapping the proximal portion of the second arm. Each of the first and second arms can include at least a partial loop member having a lumen therethrough slidably receiving the other arm, each arm further including a tissue retention member on a distal portion having a projection extending therefrom for engagement of bone or tissue when inserted therein. The staple can also include a one-way position retention assembly for allowing distal movement of each at least partial loop member relative to the other arm therethrough to tension the fastener and maintain a desired configuration.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.61/577,635 filed on Dec. 19, 2011, the disclosure of which isincorporated by reference herein.

The present disclosure is related to the following commonly assignedco-pending applications, the disclosures of which are incorporatedherein by reference: U.S. Provisional Application No. 61/577,621 filedon Dec. 19, 2011, Attorney Docket No. 10322-711.100 entitled, “APPARATUSAND METHOD FOR FORMING PILOT HOLES IN BONE AND DELIVERING FASTENERSTHEREIN FOR RETAINING AN IMPLANT”; U.S. Provisional Application No.61/577,626 filed on Dec. 19, 2011, Attorney Docket No. 10322-712.100entitled, “FASTENERS AND FASTENER DELIVERY DEVICES FOR AFFIXINGSHEET-LIKE MATERIALS TO BONE OR TISSUE” and U.S. Provisional ApplicationNo. 61/577,632 filed on Dec. 19, 2011, Attorney Docket No. 10322-713.100entitled, “FASTENERS AND FASTENER DELIVERY DEVICES FOR AFFIXINGSHEET-LIKE MATERIALS TO BONE OR TISSUE.”

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

FIELD

The present invention relates generally to orthopedic medicine andsurgery. More particularly, the present invention relates to methods andapparatus for delivery and fixation of sheet-like materials, such as fortreating tendons or like tissue of articulating joints such as tendonsin the rotator cuff of the shoulder.

BACKGROUND

The glenohumeral joint of the shoulder is found where the head of thehumerus mates with a shallow depression in the scapula. This shallowdepression is known as the glenoid fossa. Six muscles extend between thehumerus and scapula and actuate the glenohumeral joint. These sixmuscles include the deltoid, the teres major, and the four rotator cuffmuscles. The rotator cuff muscles are a complex of muscles. The musclesof the rotator cuff include the supraspinatus, the infraspinatus, thesubscapularis, and the teres minor. The centering and stabilizing rolesplayed by the rotator cuff muscles are critical to the proper functionof the shoulder. The rotator cuff muscles provide a wide variety ofmoments to rotate the humerus and to oppose unwanted components of thedeltoid and pectoral muscle forces.

The muscles of the rotator cuff arise from the scapula. The distaltendons of the rotator cuff muscles splay out and interdigitate to forma common continuous insertion on the humerus. The supraspinatus musclearises from the supraspinatus fossa of the posterior scapula, passesbeneath the acromion and the acromioclavicular joint, and attaches tothe superior aspect of the greater tuberosity. The mechanics of therotator cuff muscles are complex. The rotator cuff muscles rotate thehumerus with respect to the scapula, compress the humeral head into theglenoid fossa providing a critical stabilizing mechanism to the shoulder(known as concavity compression), and provide muscular balance. Thesupraspinatus and deltoid muscles are equally responsible for producingtorque about the shoulder joint in the functional planes of motion.

The rotator cuff muscles are critical elements of this shoulder musclebalance equation. The human shoulder has no fixed axis. In a specifiedposition, activation of a muscle creates a unique set of rotationalmoments. For example, the anterior deltoid can exert moments in forwardelevation, internal rotation, and cross-body movement. If forwardelevation is to occur without rotation, the cross-body and internalrotation moments of this muscle must be neutralized by other muscles,such as the posterior deltoid and infraspinatus. The timing andmagnitude of these balancing muscle effects must be preciselycoordinated to avoid unwanted directions of humeral motion. Thus thesimplified view of muscles as isolated motors, or as members of forcecouples must give way to an understanding that all shoulder musclesfunction together in a precisely coordinated way—opposing musclescanceling out undesired elements leaving only the net torque necessaryto produce the desired action. Injury to any of these soft tissues cangreatly inhibit ranges and types of motion of the arm.

With its complexity, range of motion and extensive use, a common softtissue injury is damage to the rotator cuff or rotator cuff tendons.Damage to the rotator cuff is a potentially serious medical conditionthat may occur during hyperextension, from an acute traumatic tear orfrom overuse of the joint. With its critical role in abduction,rotational strength and torque production, the most common injuryassociated with the rotator cuff region is a strain or tear involvingthe supraspinatus tendon. A tear at the insertion site of the tendonwith the humerus, may result in the detachment of the tendon from thebone. This detachment may be partial or full, depending upon theseverity of the injury or damage. Additionally, the strain or tear canoccur within the tendon itself. Injuries to the supraspinatus tendon andcurrent modalities for treatment are defined by the type and degree oftear. The first type of tear is a full thickness tear, which as the termindicates is a tear that extends through the thickness of thesupraspinatus tendon regardless of whether it is completely tornlaterally. The second type of tear is a partial thickness tear which isfurther classified based on how much of the thickness is torn, whetherit is greater or less than about 50% of the thickness.

The accepted treatment for a full thickness tear or a partial thicknesstear greater than 50% includes reconnecting the torn tendon via sutures.For the partial thickness tears greater than 50%, the tear is completedto a full thickness tear by cutting the tendon prior to reconnection. Incontrast to the treatment of a full thickness tear or a partialthickness tear of greater than 50%, the current standard treatment for apartial thickness tear less than 50% usually involves physical cessationfrom use of the tendon, i.e., rest. Specific exercises can also beprescribed to strengthen and loosen the shoulder area. In manyinstances, the shoulder does not heal and the partial thickness tear canbe the source of chronic pain and stiffness. Further, the pain andstiffness may cause restricted use of the limb which tends to result infurther degeneration or atrophy in the shoulder. Surgical interventionmay be required for a partial thickness tear of less than 50%, however,current treatment interventions do not include repair of the tendon, andrather the surgical procedure is directed to arthroscopic removal ofbone to relieve points of impingement or create a larger tunnel betweenthe tendon and bone that is believed to be causing tendon damage. Aspart of the treatment, degenerated tendon may also be removed using adebridement procedure in which tendon material is ablated. Again, thetendon partial thickness tear is not repaired. Several authors havereported satisfactory early post operative results from theseprocedures, but over time recurrent symptoms have been noted. In theevent of recurrent symptoms, many times a patient will “live with thepain”. This may result in less use of the arm and shoulder which causesfurther degeneration of the tendon and may lead to more extensivedamage. A tendon repair would then need to be done in a later procedureif the prescribed treatment for the partial tear was unsuccessful inrelieving pain and stiffness or over time the tear propagated throughinjury or degeneration to a full thickness tear or a partial thicknesstear greater than 50% with attendant pain and debilitation. A subsequentlater procedure would include the more drastic procedure of completingthe tear to full thickness and suturing the ends of the tendon backtogether. This procedure requires extensive rehabilitation, hasrelatively high failure rates and subjects the patient who firstpresented and was treated with a partial thickness tear less than 50% toa second surgical procedure.

As described above, adequate treatments do not currently exist forrepairing a partial thickness tear of less than 50% in the supraspinatustendon. Current procedures attempt to alleviate impingement or make roomfor movement of the tendon to prevent further damage and relievediscomfort but do not repair or strengthen the tendon. Use of the stilldamaged tendon can lead to further damage or injury. Prior damage mayresult in degeneration that requires a second more drastic procedure torepair the tendon. Further, if the prior procedure was only partiallysuccessful in relieving pain and discomfort, a response may be to usethe shoulder less which leads to degeneration and increased likelihoodof further injury along with the need for more drastic surgery. Further,it would be beneficial to be able to treat partial thickness tearsgreater than 50% without cutting the untorn portion of the tendon tocomplete the tear before suturing back together. There is a large needfor surgical techniques and systems to treat partial thickness tears andprevent future tendon damage by strengthening or repairing the nativetendon having the partial thickness tear.

SUMMARY OF THE DISCLOSURE

The present disclosure is generally directed to a fastener or staplethat can be used to attach an implant to bone or other tissue. Thestaple or fastener can be included in a kit or system that also caninclude a staple delivery device and a pilot hole forming trocarassembly. The trocar assembly is used to create pilot holes and retaininstrument position within those pilot holes for staple insertion. Thestaple delivery device can carry the staple into the pilot holes andrelease the staple in engagement with bone to retain the implant inposition.

The staple for insertion and retention in bone can include a bridgeportion having arms extending from proximate each end thereof. Thestaple can include a first arm having a proximal portion and a distalportion, a second arm having a proximal portion and a distal portion,and a bridge formed at least in part by the proximal portion of thefirst arm overlapping the proximal portion of the second arm. Each ofthe first and second arms can include at least a partial loop memberhaving a lumen therethrough slidably receiving the other arm, each armfurther including a tissue retention member on a distal portion having aprojection extending therefrom for engagement of bone when insertedtherein. The loop can be a full loop having a lumen therethrough, withthe diameter of the loop extending laterally from the arm on which it isformed or attached.

Each tissue retention member can have a lateral extent larger than thearm proximal thereto to provide a change in lateral stiffness to allowflexing of each arm adjacent the tissue retention member in response toa pullout force. Further, each projection can extend proximally andlaterally away from its respective arm. Each of the tissue retentionmembers can have a lumen extending longitudinally therethrough.

A staple of the present disclosure can also include a one-way positionretention assembly for allowing distal movement of each at least partialloop member relative to the other arm therethrough to tension thefastener and maintain a desired configuration. In some embodiments, theone-way position retention assembly can include a generally U-shapedstrap having a toothed surface along at least a portion of the lengththereof that passes through the lumen of the tissue retention membersand engages a surface therein that allows distal movement of theU-shaped strap while preventing proximal movement. Alternatively, theone-way position retention assembly can include a projection within theat least partial loop of each arm wherein the projection engages atoothed surface on the arm extending therethrough to allow distalmovement of the loop along the arm while preventing or restrictingproximal movement.

The present disclosure is also directed to a fastener delivery tool. Thefastener delivery tool can include a barrel assembly having an outersheath with a staple delivery assembly disposed therein, the stapledelivery assembly including a shaft having a distal surface for theengagement of a bridge portion of a staple when mounted on the deliverytool. The staple delivery assembly can further include a pair of staplesetting rods extending along the length of the shaft each having stakeportions extending distally beyond the distal surface.

Each stake portion can include a distal portion sized for slidingengagement of a tissue retention member and a proximal portion having asurface abutting a loop member on a staple arm for applying distallydirected force to the loop to achieve a desired configuration of thestaple retained in tissue when the stakes are moved distally relative tothe surface. The barrel can be mounted to a handle assembly fixed to theouter sheath of the barrel in operative relationship with the stapledelivery assembly.

The staple delivery assembly can be longitudinally extendable from afirst position enclosed within the sheath to a second position whereinat least a portion of the staple delivery assembly extends distally fromthe sheath. The staple delivery assembly can include a proximal shaftportion having a proximal portion of the staple setting rods fixedthereto and a distal portion with a spring therebetween to allowrelative longitudinal movement between the distal surface and the staplesetting rods in response to increased force on the proximal end of thestaple delivery assembly. Further, at least a portion of the staplesetting rods can have a cross sectional shape that slidingly engages achannel of like cross sectional shape on the staple delivery assembly torestrict relative motion of the surface and staple setting rods in thelongitudinal direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating an exemplary tissue fasteneror staple in accordance with the present disclosure;

FIG. 2 is a an alternative cross sectional plan view of the staple ofFIG. 1 depicting the components of the staple in one embodiment;

FIGS. 3A-3H are plan views of the various components that can beassembled to form the staple of FIG. 1;

FIG. 4 is a stylized anterior view of a shoulder including a humerus anda scapula;

FIG. 5 is a stylized view of a shoulder depicting the head of thehumerus shown mating with the glenoid fossa of the scapula at aglenohumeral joint and a sheet-like material is affixed to the tendon;

FIG. 6 is a stylized perspective view showing a portion of the body of ahuman patient divided into quadrants by planes for descriptive purposesherein;

FIG. 7 is a stylized perspective view illustrating an exemplaryprocedure for arthroscopic treatment of a shoulder of a patient inaccordance with one embodiment of the disclosure;

FIG. 8 is a stylized perspective view of a shoulder including asupraspinatus having a distal tendon with a sheet-like material affixedthereto;

FIG. 9A is a simplified perspective view of a tissue fastener or stapledelivery device in accordance with the present disclosure;

FIG. 9B is a simplified perspective view of a trocar assembly, includinga trocar disposed within a guide sheath assembly for creating pilotholes and retaining the sheath within the formed pilot holes fordelivery of a tissue fastener or staple by a device such as thatdepicted in FIG. 9A;

FIG. 10A is a perspective view of the sheath assembly of FIG. 9B withthe trocar removed;

FIG. 10B is a perspective view of the trocar of FIG. 9B as removed fromthe sheath assembly;

FIG. 10C is a perspective view of one pilot hole position retentionmember which is positioned in a distal portion of the sheath assembly inone embodiment of the present disclosure;

FIG. 11 is a perspective view depicting the distal portion of a stapledelivery tool or device of the present disclosure having a staplemounted thereon and a staple delivery assembly extending beyond thebarrel;

FIG. 12 is partial cross sectional perspective view of the distalportion depicted in FIG. 11 showing the surface engaging the bridge ofthe staple and staple setting rods engaging the proximal surface of thestaple loops;

FIG. 13A is simplified perspective view of a shoulder having an implantaffixed to the tendon and depicting the first step in a method ofdelivering fasteners to affix the implant to bone of the humeral head inaccordance with one method of the disclosure;

FIG. 13B is a simplified plan view of the distal portion of the trocarassembly as position to create pilot holes for affixing the implant tobone in a further step of a method of the disclosure;

FIG. 13C depicts the trocar assembly of FIG. 13B as inserted into thebone to form pilot holes in accordance with a method of the disclosure;

FIG. 13D depicts the trocar assembly with the trocar portion removed andthe remaining sheath assembly retaining its position in the pilot holesformed;

FIG. 13E depicts insertion of a fastener or staple into the formedpilots holes through the sheath assembly in accordance with a method ofthe disclosure; and,

FIG. 13F illustrates a fastener or staple as inserted in accordance witha method of the disclosure.

DETAILED DESCRIPTION

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of theinvention.

FIG. 1 is a perspective view illustrating an exemplary staple 100 inaccordance with the present detailed description. With reference to FIG.1, it will be appreciated that staple 100 may assume variousorientations without deviating from the spirit and scope of thisdetailed description. Although the various parts of this exemplaryembodiment are depicted in relative proportion to other parts of thestaple 100, other configurations in size and orientation of the variousparts are possible.

Staple 100 comprises a first arm 102A, a second arm 102B, and a bridge104. As illustrated, the bridge 104 is formed, at least in part by aportion of the first arm 102A and second arm 102B. Each arm includes adistal portion 120A, 121A and proximal portion 120B, 121B with theproximal portions of each arm overlapping the other to form a portion ofthe bridge 104. As configured, the arms can slide relative to each otheralong the proximal portions of the arms.

With continued reference to FIG. 1, each of the arms 102A, 102B includeat least a partial loop member 122A, 122B on the respective arms. Theloop may be partial or complete (as depicted in FIG. 1). In someembodiments the loop is located at the end of the proximal portion 120B,121B of each arm 102A, 102B. Each loop includes a lumen 123A, 123Bextending therethrough, respectively. A part of the proximal portion120B, 121B of the other arm is disposed through the lumen of the loopand can slide therein.

The distal portion 120A, 121A of each arm 102A, 102B includes a tissueretention member 111A, 111B. Each tissue retention member has at leastone projection 112A, 112B extending therefrom. The tissue retentionmembers can be attached to or integrally molded with a distal portion ofits respective arm 102A, 102B. As illustrated, each of the tissueretention members 111A, 111B have a lateral extent larger than the armproximal thereto to provide a change in lateral stiffness to allowflexing of each arm adjacent the tissue retention member in response toa pullout force. Further, each projection extends proximally andlaterally away from its respective arm to engage bone when placedtherein. In some embodiments of the present disclosure each tissueretention member can include a longitudinally extending lumen 114A, 114Bextending therethrough.

As also depicted in FIG. 1, a fastener of the present disclosure caninclude a one-way position retention assembly 115 for allowing distalmovement of each at least partial loop member 122A, 122B relative to theother arm therethrough to tension the fastener and maintain a desiredconfiguration. The one-way position retention assembly 115 can include agenerally U-shaped strap having a toothed surface 116 along at least aportion of the length thereof that passes through the lumen of thetissue retention members and engages a surface therein that allowsdistal movement of the U-shaped strap while preventing proximalmovement. For example, the inside surface of the tissue retentionmembers can include a projection that interacts with the toothed surfaceto allow the U-shaped strap to move distally therethrough but willprevent or restrain the U-shaped strap from moving proximally.

Alternatively, the one-way position retention assembly can include aprojection within the at least partial loop of each arm wherein theprojection engages a toothed or textured surface on the arm extendingtherethrough to allow distal movement of the loop along the arm whilepreventing proximal movement. In this embodiment the U-shaped strap isnot necessary.

In some embodiments, the components of the staple are each molded from apolymer material such as a polyether ether ketone (PEEK) or abiodegradable polymer such as polylactic acid (PLA) or polyglycolic acid(PGA) and mixtures thereof. Alternatively, staple components can be cutfrom tubular polymeric stock.

In some useful embodiments, each projection 112A, 112B of staple 100 maybe clefted to form a plurality of points for greater retention intissue. In the exemplary embodiment of FIG. 1, first projection 112Adefines a first notch 126A that divides first projection 112A into afirst sub-projection and a second sub-projection. Second projection 112Bdefines a second notch 126B. In the exemplary embodiment of FIG. 1,second notch 126B divides second projection 112B into a firstsub-projection and a second sub-projection.

Referring now to FIG. 2, the staple or fastener 100 of FIG. 1 isdepicted in cross sectional plan view to better illustrate the staplecomponents and how they are assembled to function in embodiments of thepresent disclosure. In the assembled cross sectional view of FIG. 2, thestaple 100 includes the following components: a first arm 102A; a secondarm 102B and one-way position retention assembly 115. Each of thesethree components is shown individually in partial cross sectional planview prior to assembly with the other components in FIGS. 3A-3B; FIGS.3C-3D; and, FIGS. 3E-3F, respectively. Further, the stakes of a distalportion of a staple setting rod are depicted relative to the staple asit is mounted on the stakes for insertion into bone. This component isshown individually in FIGS. 3G-3H and also described in more detail withrespect to FIGS. 11-12.

The first component of one embodiment of a staple of the presentdisclosure is a first arm 102A as noted in the assembled staple of FIG.2 and shown individually in FIGS. 3A-3B. The first arm 102A can includea length of polymeric material that is flexible and can be formed into adesired curved shape. Alternatively, the first arm 102A can be molded toa desired curved shape as depicted in FIG. 3A. In general, the first arm102A can include a distal portion 120A that can be relatively straightwith a tissue retention member 111A disposed proximate the distal end ofthe first arm 102A.

The tissue retention member 111A can include a projection or barb 112Aextending at least in part laterally from the tissue retention member inorder to contact bone and provide resistance to pullout when the stapleis under tension. Further, the tissue retention member 111A can includea longitudinally extending lumen 113A extending therethrough. Thelongitudinally extending lumen 113A can be sized for receiving a distalportion 214A of a staple setting rod 210A. The staple setting rod 210Adistal portion 214A can provide longitudinal support for the staple 100during insertion into pilot holes that have been formed in bone. Thelumen 113A can also receive a distal portion of a U-shaped member 115that, as described below, retains the staple 100 in a selectedconfiguration after deployment. As illustrated, the staple retentionmember 111A can include a lateral extent or cross section greater thanthe cross section of the arm adjacent thereto. This can result in achange in flexibility that allows the projections or barbs to bettergrasp the bone and retain position in the pilot hole.

The proximal portion 120B of the first arm 102A can be curved to form aportion of the bridge 104 of the staple 100. In some embodiments, a loop122A (which may be partial or whole) is disposed near the proximal endof the proximal portion 120B of the first arm 102A. The loop 122Aincludes at least one lumen 123A extending therethrough. As depicted,the loop includes a first lumen 127 that is spaced laterally toward thecenter of the staple inside the place of termination of the arm. Thisprovides a lumen for receiving the second arm therethrough as discussedbelow. The loop 122A also includes a second lumen 129 which extendslaterally away from the center of the staple outside the place oftermination of the arm. This lumen allows both the U-shaped member 115and the distal portion 214B of the stake 210B to extend therethrough.

The second component of one embodiment of a staple of the presentdisclosure is a second arm 102B as noted in the assembled staple of FIG.2 and shown individually in FIGS. 3C-3D. The second arm 102B can includea length of polymeric material that is flexible and can be formed into adesired curved shape. Alternatively, the second arm 102B can be moldedto a desired curved shape as depicted in FIG. 3C. In general, the secondarm 102B can include a distal portion 121A that can be relativelystraight with a tissue retention member 111B disposed proximate thedistal end of the second arm 102B.

The tissue retention member 111B can include a projection or barb 112Bextending at least in part laterally from the tissue retention member inorder to contact bone and provide resistance to pullout when the stapleis under tension. Further, the tissue retention member 111B can includea longitudinally extending lumen 113B extending therethrough. Thelongitudinally extending lumen 113B can be sized for receiving a distalportion 214B of a staple setting rod 210B. The staple setting rod 210Bdistal portion 214B can provide longitudinal support for the staple 100during insertion into pilot holes that have been formed in bone. Thelumen 113B can also receive a distal portion of a U-shaped member 115that, as described below, retains the staple 100 in a selectedconfiguration after deployment. As illustrated, the staple retentionmember 111B can include a lateral extent or cross section greater thanthe cross section of the arm adjacent thereto. This can result in achange in flexibility that allows the projections or barbs to bettergrasp the bone and retain position in the pilot hole.

The proximal portion 121B of the first arm 102B can be curved to form aportion of the bridge 104 of the staple 100. In some embodiments, a loop122B (which may be partial or whole) is disposed near the proximal endof the proximal portion 121B of the second arm 102 b. The loop 122Bincludes at least one lumen 123B extending therethrough. As depicted,the lumen 123B extends laterally away from the center of the stapleoutside the place of termination of the arm. This lumen allows theU-shaped member 115, a portion of the other arm 102A and the distalportion 214A of the stake 210A to extend therethrough.

The third component of the staple 100 can be a generally U-shaped strap115 as depicted assembled in FIG. 2 and individually as a component inFIGS. 3E-3F. As described above, the two arms of the staple includeloops through which the other arm passes. This allows the effectivelength of the arms to be changed as more or less of the two arms overlapeach other. The adjustable design allows the overall size of the stapleto be adjusted so that the bridge is in tension after insertion. Thedesign also allows the length of an individual leg to be shortened ifthe inserted leg is not engaged with sufficient holding strength in aportion of a bone that is too porous. The arm may be shortened to thepoint where the tissue retention member engages the inside surface ofthe cortical bone layer.

The U-shaped strap 115 functions to retain the staple in a selectedconfiguration. As depicted, the U-shaped strap extends over the bridge104 and includes legs that extend along the straight portions of thearms through the loops and the lumen of each tissue retention member.The U-shaped strap 115 can include a serrated or toothed surface 116that interacts with a projection within the lumen of each tissueretention member allowing the U-shaped strap to move distally relativeto the arms or the arm to move proximally relative to the U-shapedstrap. Likewise, the toothed surface prevents or restricts movement ofthe U-shaped strap proximally or the arms distally.

In one alternative embodiment, the generally U-shaped strap can beeliminated by incorporating the functional aspects of this strap intothe individual loops and arms. In particular, each of the loops caninclude a projection or other element that interacts with notches orteeth formed on the surface of the other arm passing therethrough. Thecombination would allow the overall length of the staple or individualarm length to be shortened while restricting or preventing each arm fromlengthening.

A cross section of a portion of the stakes 210A, 210B are depicted inFIGS. 3G-3H. The stakes include a distal portion 214A, 214B of smallercross section than a proximal portion 212A, 212B. As illustrated in FIG.2, the distal portions 214 extend through the loops of the arms and thelumens of the tissue retention members. The cross section of theproximal portion 212 is larger than the lumen of the loop so that aproximal surface of the loop abuts a distal surface of the proximalportion 212 of the stake 210. Force applied to the interface betweenthese surfaces causes either the bridge to move distally or the tissueretention member opposite the loop to move proximally. As previouslystated, this motion allows the staple to be configured after beingplaced in the pilot holes so that the bridge is in tension while theprojections of the tissue retention members are engaged sufficiently incompetent bone material.

Next referring to FIG. 4, an exemplary use or application of the staplesof the present disclosure is described. FIG. 4 is a stylized anteriorview of a patient 20. For purposes of illustration, a shoulder 22 ofpatient 20 is shown in cross-section in FIG. 4. Shoulder 22 includes ahumerus 14 and a scapula 12. In FIG. 4, a head 24 of humerus 14 can beseen mating with a glenoid fossa of scapula 12 at a glenohumeral joint.With reference to FIG. 4, it will be appreciated that the glenoid fossacomprises a shallow depression in scapula 12. The movement of humerus 14relative to scapula 12 is controlled by a number of muscles including:the deltoid, the supraspinatus, the infraspinatus, the subscapularis,and the teres minor. For purposes of illustration, only thesupraspinatus 26 is shown in FIG. 4.

With reference to FIG. 4, a distal tendon 28 of the supraspinatus 26meets humerus 14 at an insertion point. Scapula 12 of shoulder 22includes an acromium 32. In FIG. 4, a subacromial bursa 34 is shownextending between acromium 32 of scapula 12 and head 24 of humerus 14.Subacromial bursa 34 is shown overlaying supraspinatus 26 as well assupraspinatus tendon 28 and a portion of humerus 14. Subacromial bursa34 is one of the hundreds of bursae found the human body. Each bursacomprises a fluid filled sac. The presence of these bursae in the bodyreduces friction between bodily tissues.

The exemplary staples or fasteners described herein may be used to affixtendon repair implants to various target tissues. The shoulder depictedin FIG. 4 is one example where a tendon repair implant may be affixed toone or more bones associated with an articulating joint, such as theglenohumeral joint. Additionally, the tendon repair implant may beaffixed to one or more tendons to be treated. The tendons to be treatedmay be torn, partially torn, have internal micro-tears, be untorn,and/or be thinned due to age, injury or overuse. Applicants believe thatthe methods and apparatus of the present application and related devicesmay provide very beneficial therapeutic effect on a patient experiencingjoint pain believed to be caused by partial thickness tears and/orinternal microtears. By applying a tendon-repair implant early before afull tear or other injury develops, the implant may cause the tendon tothicken and/or at least partially repair itself, thereby avoiding moreextensive joint damage, pain, and the need for more extensive jointrepair surgery.

FIG. 5 is a stylized anterior view of a shoulder 22 including a humerus14 and a scapula 12. In FIG. 5, a head 24 of humerus 14 is shown matingwith a glenoid fossa of scapula 12 at a glenohumeral joint. Asupraspinatus 26 is also shown in FIG. 5. This muscle, along withothers, controls the movement of humerus 14 relative to scapula 12. Adistal tendon 28 of supraspinatus 26 meets humerus 14 at an insertionpoint 30.

As depicted in FIG. 5, distal tendon 28 includes a first damaged portion36. A number of loose tendon fibers 40 in first damaged portion 36 arevisible in FIG. 5. First damaged portion 36 includes a first tear 42extending partially through distal tendon 28. First tear 42 maytherefore be referred to as a partial thickness tear. With reference toFIG. 5, first tear 42 begins on the side of distal tendon 28 facing thesubacromial bursa (shown in the previous Figure) and ends midway throughdistal tendon 28. Accordingly, first tear 42 may be referred to as abursal side tear.

With reference to FIG. 5, distal tendon 28 includes a second damagedportion 38 located near insertion point 30. As illustrated, seconddamaged portion 38 of distal tendon 28 has become frayed and a number ofloose tendon fibers 40 are visible. Second damaged portion 38 of distaltendon 28 includes second tear 44. Second tear 44 begins on the side ofdistal tendon 28 facing the center of the humeral head 24. Accordingly,second damaged portion 38 may be referred to as an articular side tear.

FIG. 5 illustrates a sheet-like implant 50 has been placed over thebursal side of distal tendon 28. The sheet-like implant 50 is affixed todistal tendon 28 by a plurality of tendon staples 51. Sheet-like implant50 is affixed to humerus 14 by a plurality of bone staples 100 inaccordance with designs of staples disclosed herein. Sheet-like implant50 extends over insertion point 30, first tear 42 and second tear 44.Some useful methods in accordance with this detailed description mayinclude placing a tendon repair implant on the bursal side of a tendonregardless of whether the tears being treated are on the bursal side,articular side or within the tendon. In some cases the exact locationand nature of the tears being treated may be unknown. A tendon repairimplant may be applied to the bursal side of a tendon to treat shoulderpain that is most likely caused by one or more partial thickness tearsin the tendon.

FIG. 6 is a stylized perspective view showing a portion of the body 82of a human patient 20. Body 82 includes a shoulder 22. In the exemplaryembodiment of FIG. 6, a plurality of cannulas are positioned to access atreatment site within shoulder 22. In some cases, shoulder 22 may beinflated by pumping a continuous flow of saline through shoulder 22 tocreate a cavity proximate the treatment site. The cannulas shown in FIG.6 include a first cannula 80A, a second cannula 80B and a third cannula80C.

In FIG. 6, a sagital plane SP and a frontal plane FP are shownintersecting body 82. Sagital plane SP and frontal plane FP intersectone another at a medial axis MA of body 82. With reference to FIG. 6,sagital plane SP bisects body 82 into a right side 84 and a left side86. Also with reference to FIG. 6, frontal plane FP divides body 82 intoan anterior portion 92 and a posterior portion 88. Sagital plane SP anda frontal plane FP are generally perpendicular to one another. Theseplanes and portions are used to describe the procedures used inexemplary embodiments.

First cannula 80A is accessing a treatment site within shoulder 22 usinga lateral approach in which first cannula 80A pierces the outer surfaceof right side 84 of body 82. The term lateral approach could also beused to describe situations in which an instrument pierces the outersurface of left side 86 of body 82. Second cannula 80B is accessing atreatment site within shoulder 22 using a posterior approach in whichsecond cannula 80B pierces the outer surface of posterior portion 88 ofbody 82. Third cannula 80C is accessing a treatment site within shoulder22 using an anterior approach in which third cannula 80C pierces theouter surface of anterior portion 92 of body 82.

FIG. 7 is a stylized perspective view illustrating an exemplaryprocedure for treating a shoulder 22 of a patient 20. The procedureillustrated in FIG. 7 may include, for example, fixing tendon repairimplants to one or more tendons of shoulder 22. The tendons treated maybe torn, partially torn, have internal micro-tears, be untorn, and/or bethinned due to age, injury or overuse.

Shoulder 22 of FIG. 7 has been inflated to create a cavity therein. Afluid supply 52 is pumping a continuous flow of saline into the cavity.This flow of saline exits the cavity via a fluid drain 54. A camera 56provides images from inside the cavity. The images provided by camera 56may be viewed on a display 58.

Camera 56 may be used to visually inspect the tendons of shoulder 22 fordamage. A tendon repair implant in accordance with this disclosure maybe affixed to a bursal surface of the tendon regardless of whether thereare visible signs of tendon damage. Applicants believe that the methodsand apparatus of the present application and related devices may providevery beneficial therapeutic effect on a patient experiencing joint painbelieved to be caused by internal microtears, but having no clear signsof tendon tears. By applying a tendon repair implant early before a fulltear or other injury develops, the implant may cause the tendon tothicken and/or at least partially repair itself, thereby avoiding moreextensive joint damage, pain, and the need for more extensive jointrepair surgery.

An implant delivery system 60 can be seen extending from shoulder 22 inFIG. 7. Implant delivery system 60 is extending through a first cannula80A. In certain embodiments, first cannula 80A can access a treatmentsite within shoulder 22 using a lateral approach in which first cannula80A pierces the outer surface of a right side of the patient's body. Insome cases a physician may choose not to use a cannula in conjunctionwith implant delivery system 60. When that is the case, the implantdelivery system may be advanced through tissue. Implant delivery system60 comprises a sheath that is affixed to a handle. The sheath defines alumen and a distal opening fluidly communicating with the lumen. In theembodiment of FIG. 7, the distal opening of the sheath has been placedin fluid communication with the cavity created in shoulder 22.

A tendon repair implant is at least partially disposed in the lumendefined by the sheath of implant delivery system 60. Implant deliverysystem 60 can be used to place the tendon repair implant inside shoulder22. In some embodiments, the tendon repair implant is folded into acompact configuration when inside the lumen of the sheath. When this isthe case, implant delivery system 60 may be used to unfold the tendonrepair implant into an expanded shape. Additionally, implant deliverysystem 60 can be used to hold the tendon repair implant against thetendon.

The tendon repair implant may be affixed to the tendon while it is heldagainst the tendon by implant delivery system 60. Various attachmentelements may be used to fix the tendon-repair implant to the tendon.Examples of attachment elements that may be suitable in someapplications include sutures, tissue anchors, bone anchors, and staples.In the exemplary embodiment of FIG. 7, the shaft of a fixation tool 70is shown extending into shoulder 22. In one exemplary embodiment,fixation tool 70 is capable of fixing the tendon repair implant to thetendon and bone with one or more staples of the present disclosure whilethe tendon repair implant may held against the tendon by implantdelivery system 60.

FIG. 8 is a stylized perspective view of a shoulder 22 including asupraspinatus 26 having a distal tendon 28. With reference to FIG. 8, atendon repair implant 50 has been affixed to a surface of distal tendon28. Tendon repair implant 50 may comprise, for example, varioussheet-like structures without deviating from the spirit and scope of thepresent detailed description. In some useful embodiments, the sheet-likestructure may comprise a plurality of fibers. The fibers may beinterlinked with one another. When this is the case, the sheet-likestructure may comprise a plurality of apertures comprising theinterstitial spaces between fibers. Various processes may be used tointerlink the fibers with one another. Examples of processes that may besuitable in some applications including weaving, knitting, and braiding.In some embodiments, the sheet-like structure may comprise a laminateincluding multiple layers of film with each layer of film defining aplurality of micro-machined or formed holes. The sheet-like structure ofthe tendon repair implant may also comprise a reconstituted collagenmaterial having a porous structure. Additionally, the sheet-likestructure of the tendon repair implant may also comprise a plurality ofelectro-spun nanofiber filaments forming a composite sheet.Additionally, the sheet-like structure may comprise a synthetic spongematerial that defines a plurality of pores. The sheet-like structure mayalso comprise a reticulated foam material. Reticulated foam materialsthat may be suitable in some applications are available from BiomerixCorporation of Fremont, Calif. which identifies these materials usingthe trademark BIOMATERIAL™. The sheet-like structure may be circular,oval, oblong, square, rectangular, or other shape configured to suit thetarget anatomy.

Various attachment elements may be used to fix tendon repair implant 50to distal tendon 28 without deviating from the spirit and scope of thisdetailed description. Examples of attachment elements that may besuitable in some applications include sutures, tissue anchors, boneanchors, and staples. In the embodiment of FIG. 9, sheet-like implant 50is affixed to distal tendon 28 by a plurality of tendon staples 51.Sheet-like implant 50 is affixed to humerus 14 by a plurality of bonestaples 100 as described with respect to the exemplary embodiment ofFIG. 1 and detailed throughout this disclosure.

In some exemplary methods, a plurality of staples may be applied using afixation tool. After the staples are applied, the fixation tool may bewithdrawn from the body of the patient. Distal tendon 28 meets humerus14 at an insertion point 30. With reference to FIG. 8, it will beappreciated that sheet-like implant 50 extends over insertion point 30.Tendon repair implant may be applied to distal tendon 28, for example,using the procedure illustrated in the previous figures. In variousembodiments, staples may straddle the perimeter edge of the sheet-likeimplant (as shown in FIG. 8), may be applied adjacent to the perimeter,and/or be applied to a central region of the implant. In someembodiments, the staples may be used to attach the implant to softtissue and/or to bone.

Staples or fasteners 100, as exemplified in FIG. 1 and described andillustrated herein can be used to attach tissue and implants to bone. Inat least some embodiments, the staple is generally flexible and includesareas of relative lateral weakness on the portions of the arms. Asdescribed above, these areas of increased flexibility provide improvedstaple retention as these portions allow flexing and bending in responseto increasing pullout forces. With this flexibility, the fastenerscannot be pounded or driven into bone or other tissue as a conventionalhard staple would be driven into paper, wood, tissue or bone. Therefore,for application of the staple of the present disclosure to affixingtissue or implants to bone, the staple is generally included in a kitthat also includes a staple delivery device 200 and a pilot hole formingtrocar assembly 300, as schematically illustrated in FIGS. 9A and 9B,respectively.

In general, the staple delivery device 200 can include a handle assembly201 and a barrel assembly 205. The handle assembly 201 includes atrigger 203 that is operatively coupled to mechanisms in the barrelassembly 205 to deploy a staple of the present disclosure in bone. Thestaple delivery device 200 can be used in conjunction with the pilothole forming trocar assembly 300 of FIG. 9B.

The pilot hole forming trocar assembly 300, illustrated generally inFIG. 9B includes a trocar 302 and a position retention sleeve 304. Thetrocar 302 is releasably coupled to the position retention sleeve 304and slides in keyed arrangement within the sleeve 304 when uncoupled.The trocar 302 includes a distal portion having a retractable blade 306and a pair of pilot hole forming spikes 308 extending distally from thetrocar shaft. The retractable blade 306 is useful in inserting theassembly through an incision. The retractable blade 306 can be retractedin this exemplary embodiment by activating release button 315 whichcauses a spring (not shown) to pull the retractable blade 306 into theshaft of the trocar within the position retention sleeve 304. In thisposition, the pilot hole forming spikes remain extended from the shaft.In some embodiments the retractable blade 306 can be omitted if thepilot hole forming trocar assembly is to be inserted into an incisionthat already has a cannula extending therethrough to provide aninstrument path.

Referring to FIGS. 10A-10C, details of the elements of one exemplaryembodiment of a pilot hole forming trocar assembly 300 are illustrated.The pilot hole forming trocar assembly is used to created pilot holes ina bone for subsequent placement of a staple or fastener, such as staple100 of FIG. 1. Further, the pilot hole forming trocar assembly includesa means for retaining instrument position with respect to the pilotholes when the trocar is removed so that a staple delivery device 200can be inserted and the staple be in alignment with the already formedpilot holes. This prevents the time and difficulty associated withfinding the pilot holes with the staple, which in fact may not bepossible for many practitioners.

As previously stated, a pilot hole forming trocar assembly 300 caninclude a trocar 302 and a position retention sleeve 304. One embodimentof a position retention sleeve 304 is illustrated in FIG. 10A. Theposition retention sleeve 304 includes a shaft 311 having a lumen 310extending therethrough. The lumen 310 is sized to receive the trocar 302when used to form pilot holes. The lumen 310 is also sized to receive astaple delivery device 200 when used to position a staple in pilot holeformed in bone. The lumen is shaped or keyed to cooperate with either ofthese instruments or other instruments so that relative rotationalposition of the trocar 302 or staple delivery device 200 is fixed whenslidably positioned in the position retention sleeve. An opening orwindow 313 may be included near the distal end of the position retentionsleeve to allow viewing of devices inserted therein.

Position retention members 314 extend distally from the shaft 311. Asdetailed in FIG. 10C, the position retention members can be included onan insert 312 that is affixed proximate the distal end of the shaft 311.Alternatively, the position retention members can be integral to theshaft 311. The position retention members are sized and designed toextend into pilot holes as they are formed by the trocar 302 describedbelow. When the trocar 302 is removed, the position retention members314, along with the sleeve 311 remain in position to provide a guide forthe staple delivery device 200 to be inserted into proper position andposition a staple 100 in the pilot holes. As depicted, the positionretention members 314 can include longitudinally extendingsemi-cylindrical projections. In the disclosed embodiment, the pilothole forming spikes 308 of the trocar 302 slide within the partiallumens of the position retention members 314. This design can providesupport for the spikes as they are pounded into bone and can also allowthe position retention members to readily slide into pilot holes formedby the spikes 308.

A more detailed depiction of one alternative embodiment of a trocar 302is included in FIG. 10B. The trocar includes a shaft 320 having at itsproximal end a knob 324 that can be used to pound or push the trocar 302into bone. The trocar can further include a collar 322 which can be usedto releasable engage the position retention sleeve 304 when the two aremated for forming pilot holes. A spring 323 can be included which causesor aids the retraction of the trocar when it is released from theposition retention sleeve.

As previously disclosed, the distal end of the trocar 302 includes twopilot hole forming spikes 308 extending from shaft 320. A retractableblade 306 is positioned between the spikes 308. In use, the blade 306 isretracted prior to the spikes 308 being used to form pilot holes inbone.

Now referring to FIG. 11, a distal portion of a staple delivery device200, in particular a distal portion of the barrel 205 of FIG. 9A isdepicted with a staple 100 mounted thereon for delivery into bone. Theparts of the staple are labeled as they are in FIG. 1 with all of thesame components numbered the same. In FIG. 11, the barrel 205 has anouter sheath 206 with a staple delivery assembly 207 disposed within thelumen of the sheath 206. The staple delivery assembly 207 can be movedfrom a retracted position within the sheath 206 to an extended positiondistal of the sheath 206, as illustrated.

FIG. 12 is a cross sectional view of the distal portion of the stapledelivery device 200 depicted in FIG. 11. The staple delivery assembly207 is illustrated within the lumen of the sheath 206. As seen in bothfigures, the staple setting rods 210A, 210B have a portion extendingbeyond the sheath onto which the staple is mounted and carried fordelivery. Further, the staple delivery assembly 207 includes a spring208 engaging a staple pusher 219 having a distal surface 220 engagingthe bridge 104. This portion of the staple delivery assembly 207 urgesthe staple 100 into pilot holes.

The staple setting rods 210 have a proximal portion 212 that includesdistal surfaces in abutment with the proximal surfaces of the loops 122.The staple setting rods are actively coupled to the trigger 203 and canbe urged distally when the staple is in position. As previouslydiscussed, this action adjusts the staple configuration so that thebridge is in tension and the staple retention members are engaged incompetent bone to provide adequate holding strength.

The method of forming pilot holes and delivering staples of the presentdisclosure to bone is described with respect to FIGS. 13A-13F whichdepict the various steps in affixing an implant 50 to bone with staplesor fasteners of the present disclosure. FIG. 13A schematically depicts ashoulder 22 of a patient 20 having an implant 50 positioned over asupraspinitus tendon 28. The implant is partially affixed to the tendon28 with fasteners 51 and extends laterally to and over the insertionpoint of the tendon to the humeral head 24. As depicted, the implant 50is not yet affixed to the humeral head 24. A distal portion of a pilothole forming trocar assembly 300, in particular the position retentionsleeve 304, is disposed over a desired location near the lateral edge ofthe implant 50 where it overlies the humeral head 24. It is noted theFIG. 13A is a depiction with all overlying tissue removed from theshoulder 22 to clearly show the location of the entire implant 50 on thesupraspinitus tendon 28. This view is not possible during actualarthroscopic procedures in which the fasteners and instruments of thepresent disclosure can be used, however the depiction provides a clearunderstanding of the placement of an implant and the use of fastenersdisclosed herein. In actual use the surgeon will have a side view from aviewing scope (not shown) of a small space created by inflating the areawith fluid and clearing necessary obstructions from the implant area.

FIG. 13B is a schematic illustration of a cross-sectional side view ofthe partially affixed implant of FIG. 13A showing the small portion ofthe implant 50 that is not yet affixed to the humeral head 24. As can beseen in the illustration, the humeral head 24 is shown in cross-sectionwhich illustrates the composite nature of bone structure. In general,bone includes hard outer portion or cortical layer 375 and a poroussofter inner portion or cancellous bone 376. The pilot hole formingtrocar assembly 300 is positioned with the spikes 308 over a selectedposition on the implant 50. As previously discussed, the trocar 302 ispositioned within the lumen of the position retention sleeve 304 withspikes 308 extending distally. The spikes 308 can be used to manipulateand position the implant as needed. Once in position, the spikes 308 canbe driven into the bone.

Referring to FIG. 13C, the illustration of FIG. 13B is re-illustratedwith the pilot hole forming trocar 300 spikes pounded or otherwisedriven into the humeral head 24, penetrating the cortical layer 375 intothe cancellous portion 376. As illustrated, position retention members314 also penetrate the bone with the spikes 308. In FIG. 13D, it isillustrated that the trocar 302 and its distal spikes 308 are nowremoved leaving formed pilot holes 309 with the position retentionsleeve 304 remaining in position with position retention member 314extending into pilot holes 309. The position retention member 304 lumenprovides a guide to the pilot holes 309 for a staple delivery device200. In FIG. 13E, a staple 100 is shown extending into the pilot holes309 as mounted on the distal end of a staple delivery device 200 thathas been inserted into the lumen of position retention member 304. Inthis position the staple can be delivered and retained in the bone aspreviously described in the various embodiments disclosed herein. Indelivering the staple 100, the staple delivery assembly distal surfacepushes on the bridge of the staple while the proximal portion of thestaple setting rods is urged distally relative to the surface. Thisaction of the staple delivery assembly on the proximal surface of theloop of each leg will caused the staple to adjust to a tensionedconfiguration. Two adjustments may occur. First, the proximal portion ofthe arms may draw down on the implant. Second, if either of the stapleretention members are not secure in bone, they will move proximallywithin the pilot hole until bone is grasped and counters the force onthe proximal surface of the loop. This may include the staple retentionmember moving proximally to the interface between cancellous andcortical bone, particularly if the staple is placed in a more porousbone structure, such as in an elderly person. FIG. 13F depicts a staple100 as delivered into bone with bridge 304 holding the implant inposition on the bone and arms of the staple retaining position in the inthe bone, such as within the cancellous portion 376.

While exemplary embodiments of the present invention have been shown anddescribed, modifications may be made, and it is therefore intended inthe appended claims and subsequently filed claims to cover all suchchanges and modifications which fall within the true spirit and scope ofthe invention.

What is claimed is:
 1. A fastener for attachment to bone or tissuecomprising: a first arm having a proximal portion and a distal portion,a second arm having a proximal portion and a distal portion, and abridge formed at least in part by the proximal portion of the first armoverlapping the proximal portion of the second arm, wherein each of thefirst and second arms include at least a partial loop member having alumen therethrough slidably receiving the other arm, each arm furtherincluding a tissue retention member on a distal portion having aprojection extending therefrom; and, a one-way position retentionassembly for allowing distal movement of each at least partial loopmember relative to the other arm therethrough to tension the fastenerand maintain a desired configuration.
 2. The fastener of claim 1,wherein each tissue retention member has a lateral extent larger thanthe arm proximal thereto to provide a change in lateral stiffness toallow flexing of each arm adjacent the tissue retention member inresponse to a pullout force.
 3. The fastener of claim 1, wherein eachprojection extends proximally and laterally away from its respectivearm.
 4. The fastener of claim 2, wherein each of the tissue retentionmembers have a lumen extending longitudinally therethrough.
 5. Thefastener of claim 4, wherein the one-way position retention assemblycomprises a generally U-shaped strap having a toothed surface along atleast a portion of the length thereof that passes through the lumen ofthe tissue retention members and engages a surface therein that allowsdistal movement of the U-shaped strap while preventing proximalmovement.
 6. The fastener of claim 4, wherein the one-way positionretention assembly comprises a projection within the at least partialloop of each arm wherein the projection engages a toothed surface on thearm extending therethrough to allow distal movement of the loop alongthe arm while preventing proximal movement.
 7. The fastener of claim 1,wherein the first arm, the second arm and the bridge are each formed ofa polymeric material.
 8. The fastener of claim 7, wherein the polymericmaterial comprises a polyether ether ketone (PEEK) material.
 9. A staplefor insertion and retention in bone or tissue comprising: a first armhaving a proximal portion and a distal portion, a second arm having aproximal portion and a distal portion, and a bridge formed at least inpart by the proximal portion of the first arm overlapping the proximalportion of the second arm, wherein each of the first and second armsinclude a laterally extending loop having a lumen slidably receiving aportion of the other arm therethrough, each arm further including atissue retention member on a distal portion thereof; and, a generallyU-shaped strap having a toothed surface along at least a portion of thelength thereof that engages a surface of each arm and allows distalmovement of the U-shaped strap while preventing proximal movement. 10.The fastener of claim 9, wherein each tissue retention member has alateral extent larger than the arm proximal thereto to provide a changein lateral stiffness to allow flexing of each arm adjacent the tissueretention member in response to a pullout force.
 11. The fastener ofclaim 9, wherein each projection extends proximally and laterally awayfrom its respective arm.
 12. The fastener of claim 9, wherein each ofthe tissue retention members has a lumen extending longitudinallytherethrough.
 13. The fastener of claim 12, wherein the generallyU-shaped strap toothed surface passes through the lumen of each of thetissue retention members and engages a surface therein that allowsdistal movement of the U-shaped strap while preventing proximalmovement.
 14. A fastener delivery tool comprising: a barrel assemblyhaving an outer sheath with a staple delivery assembly disposed therein,the staple delivery assembly including a shaft having a distal surfacefor the engagement of a bridge portion of a staple when mounted on thedelivery tool; the staple delivery assembly further including a pair ofstaple setting rods extending along the length of the shaft each havingstake portions extending distally beyond the distal surface, whereineach stake portion includes a distal portion sized for slidingengagement of a tissue retention member and a proximal portion having asurface abutting a loop member on a staple arm for applying distallydirected force to the loop to achieve a desired configuration of thestaple retained in tissue when the stakes are moved distally relative tothe surface; and, a handle assembly fixed to the outer sheath of thebarrel in operative relationship with the staple delivery assembly. 15.The fastener delivery tool of claim 14, wherein the staple deliveryassembly is longitudinally extendable from a first position enclosedwithin the sheath to a second position wherein at least a portion of thestaple delivery assembly extends distally from the sheath.
 16. Thefastener delivery tool of claim 14, wherein the staple delivery assemblyincludes a proximal shaft portion having a proximal portion of thestaple setting rods fixed thereto and a distal portion with a springtherebetween to allow relative longitudinal movement between the distalsurface and the staple setting rods in response to increased force onthe proximal end of the staple delivery assembly.
 17. The fastenerdelivery tool of claim 16, wherein at least a portion of the staplesetting rods have a cross sectional shape that slidingly engages achannel of like cross sectional shape on the staple delivery assembly torestrict relative motion of the surface and staple setting rods in thelongitudinal direction.